1. Field of the Invention
The invention relates to the use of macrocyclic metal ligand complexes as bleaching catalysts, and more particularly, to transition metal complexes of macrocyclic tetraamide ligands as catalysts for enhancing oxidative bleaching reactions.
2. Brief Statement on Related Art
Hydrogen peroxide, and other peroxy compounds which yield hydrogen peroxide in aqueous solution, have long been known for use in fabric and surface bleaching. However, peroxy compounds, such as sodium perborate (monohydrate or tetrahydrate), sodium percarbonate, and the like, have relatively mild bleaching performance at low temperatures (e.g., below 100.degree. C./38.8.degree. F.). Organic peroxyacids, such as perbenzoic acid, are stronger oxidants, but are often unstable unless stabilized by costly and cumbersome methods. In addition, the premade peroxyacids are often cost-ineffective to manufacture. Bleach activators, or peracid precursors, such as esters, ketones, nitrites, or the like, are often effective at enhancing the efficacy of peroxy compounds. However, the bleach activators must usually be present in stoichiometric or greater quantities and can also be costly to manufacture.
Transition metal chelates, especially those using manganese and iron, are known as bleaching catalysts for peroxy compounds. These are represented by, for example, Favre et al., U.S. Pat. No. 5,246,621, Bragg et al., U.S. Pat. No. 5,002,682, Postlethwaite, U.S. Pat. No. 4,119,557, and Ellis, Jr et al., U.S. Pat. No. 4,900,871. These transition metal chelates can be used, for example, in laundering fabrics with an appropriate peroxy compound, for example, sodium perborate monohydrate.
While these transition metal chelates have been proven to improve the oxidizing power of peroxy compounds, they sometimes can mediate dye and, even damage, to fabrics when used as bleaching activators.
Certain transition metal chelates have been researched for unrelated purposes. For example, complexes of high oxidation state transition metals are known to function as oxidants in numerous biological reactions under the influence of a protein matrix and in recent years a widespread interest in understanding the mechanism of action and the reactivity of certain monooxygenase catalysts has developed.
An exemplary program is described in Collins, T. J., "Designing Ligands for Oxidizing Complexes," Accounts of Chemical Research, 279, Vol. 27, No. 9 (1994). This article lays out a design oriented approach for obtaining ligands that are resistant to oxidative degradation when coordinated to highly oxidizing metal centers. Several diamido-N-diphenoxido and diamido-N-alkoxido acyclic chelate compounds and macrocyclic tetraamido-N chelate compounds are described in the Collins Accounts of Chemical Research article.
An azide based synthetic route to macrocyclic tetraamido ligands is described in Uffelman, E. S., Ph.D. Thesis, California Institute of Technology, (1992). Additionally, synthesis of an aryl bridged tetraamido ligand via the azide based route can proceed by using an aromatic diamine as a starting material.
However, the art has not recognized that certain macrocyclic tetraamido ligands will provide novel and unusually effective bleach activators for peroxy compounds. Additionally, it has not been taught, disclosed or suggested that these types of compounds will be unusually advantageous in the areas of dye transfer inhibition, anti-soil redeposition and stain removal.